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Primary vs Secondary Growth-3 |
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Secondary Growth refers to tissues produced by Lateral Meristems.There are two Lateral Meristems.
These are the These cause an increase in the width or girth of organs, rather than an increase in length. As you might expect, the Vascular Cambium produces Vascular Tissues. The Cork Camium produces CorK!
We will consider the Vascular Cambium first. |
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Imagine a round sheet of rolled cookie dough (procambium). Two people start to cut out cookies at opposite Poles. One person is cutting Squares (Phloem) while the other is cutting Circles (Xylem). As they progress, the only uncut dough will be located between them. If their arms are too short to reach all the way to the center, the dough in this area will remain uncut (a.k.a. undifferentiated).This is the Vascular Cambium. The Vascular Tissues which develop directly from the Procambium are said to be Primary Tissues (primary Phloem & Primary Xylem).
Once More with Feeling!!!!!!!! The cookie dough is Procambium. The Circles are Xylem & the Squares are Phloem. The remaining uncut dough is the Vascular Cambium.
The Vascular Cambium is Meristematic.This means that it is still dividing. P3ericlinal Divisions predominate in the Vascular Cambium. Periclinal Divisions occur such that the new Cell Wall is parallel to the surface of the Stem. This is differnt than the planes of division in Procambium. Periclinal Divisions produce Radial Files of Cells. Radial means that the cell files are parallel to a radius drawn from the center of the stem towards the outside of the stem. Derivatives of the Vascular Cambium The Vascular Cambium can remain active for Centuries in some plants like the Redwood or Koa!!!! |
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Remember that Procambium is a Primary Meristem.
Yes Drill Sargent!! How could I possibly forget that! 
